Envelope oxygenator for blood having inflatable portions and process of using same

ABSTRACT

A BLOOD OXYGENATOR WHICH DEFINES A FLOW PASSAGE, AND HAVING MEANS FOR INTRODUCING A STREAM OF BLOOD INTO ONE END OF THE FLOW PASSAGE AND MEANS FOR REMOVING BLOOD FROM THE OTHER END. THE OXYGENATOR HAS MEANS DEFINING A FLUID PRESSURIZABLE SECTION TO PROVIDE DIMENSIONAL STABIL-   ITY THERETO, FOR EXAMPLE, TO CONTROL THE CROSS SECTIONAL AREA OF THE OXYGENATING PORTION OF THE FLOW PASSAGE OR T MAKE THE OXYGENATOR SELF-SUPPORTNG.

Apml 24, 1973 R. J. LEONARD 3,729,377

ENVELOPE OXYGENATOR FOR BLOOD HAVING INFLATABLE PORTIONS AND PROCESS OF USING SAME Filed March 12, 1971 3 Sheets-Sheet l fizz/Ha ar April 24, 1973 R. J. LEONARD 3,729,377

ENVELOPE OXYGENATOR FOR BLOOD HAVING INFLATABLE PORTIONS AND PROCESS OF USING SAME Filed March 12, 1971 5 Sheets-Sheet 2 Ap 1 R. J. LEONARD 3, 29, 7

. VELOPE OXYGENATOR FOR BLOOD HAVING INFLATABLE PORTIONS AND PROCESS OF USING SAME Filed March 12, 1971 5 Sheets-Sheet 5 fa malfLc'awza/rzi United States Patent O ENVELOPE OXYGENATOR FOR BLOOD HAVING INFLATABLE PORTIONS AND PROCESS OF USING SAME Ronald J. Leonard, Elk Grove Village, 111., assignor to Baxter Laboratories, Inc., Morton Grove, Ill. Filed Mar. 12, 1971, Ser. No. 123,518 Int. Cl. A61m 1/03; C121: 9/00 US. Cl. 1951.8 12 Claims ABSTRACT OF THE DISCLOSURE A blood oxygenator which defines a flow passage, and having means for introducing a stream of blood into one end of the flow passage and means for removing blood from the other end. The oxygenator has means defining a fluid pressurizable section to provide dimensional stability thereto, for example, to control the cross sectional area of the oxygenating portion of the flow passage or to make the oxygenator self-supporting.

BACKGROUND OF THE INVENTION Bubble type blood oxygenators are commercially avail able at the present time, and are used as a component of heart-lung machines in open heart surgery and the like. Basically, an envelope or casing is used which defines a flow passage for blood and oxygen. The flow passage includes an oxygenating column portion of the flow passage in which tiny bubbles of oxygen from a sparger are mixed with blood, and a defoaming portion of the flow passage to remove all gas bubbles from the blood prior to its readministration to the patient.

The presently known plastic film envelope type blood oxygenators are generally non-self-supporting, so they must be strung to a rigid frame about at least three sides in order to provide the dimensional stability which is necessary for the best operation.

Furthermore, the portion of the blood flow path which constitutes the oxygenating column has previously been of transverse dimension which is governed by the spacing of heat seals defining the column in the plastic envelope of that type of blood oxygenator, or is constructed to be of unvarying transverse dimension in rigid oxygenators. Several undesirable results occur because of this conventional structure.

During operation of the blood oxygenator, the bloodgas mixture in the oxygenating column has a density less than that of blood, and must have a predetermined upward velocity and a predetermined ratio of blood to gas in order to obtain a level of oxygenation of the blood falling between specific, necessary upper and lower limits. The above factors are, of course, dependent upon the rate of blood flow into the bottom of the oxygenation column and the rate of oxygen flow into the column.

However, during the course of operation, the rate of blood flow from the patient into the oxygenation column may vary fairly substantially. Hitherto, the necessary response was to reduce or increase the amount of oxygen passing into the blood column. However, the result of an oxygen flow reduction is to reduce the ratio of oxygen gas in the column compared with the amount of blood, which may cause the blood to poo in the column. By this latter term it is meant that the upward velocity of the blood becomes undesirably slow, and its residence time in the oxygenating column to high, because of a decrease in the amount of oxygen gas present in the column and a resultant increase in the amount of blood in the column. An oxygen flow reduction will also cause an increase in the density of the blood-gas mixture in the column, which causes flexible plastic column walls to stretch, increasing the volume of the column and thus further reducing the upward velocity of blood. Such a density increase also increases the back pressure produced by the column of blood on the blood inlet to the column, which can be highly undesirable. The pooling of blood in the oxygenation column also undesirably increases the amount of blood outside of the patients body.

DESCRIPTION OF THE INVENTION In accordance with this invention, the above various disadvantages of the conventional blood oxygenators are remedied by furnishing means defining a fluid pressurizable section as part of the oxygenator to provide desired structural or dimensional stability thereto, which structure can be stabilized in variable dimensional configurations as desired.

In one aspect of this invention, the fluid pressurizable section is used to provide dimensional stability through positive control of the cross sectional area of the oxygenating column, to vary the volume of the column as desired. Thus, upon a change in the blood flow rate into the bottom of the oxygenating column, an alternative course of action is available to the conventional expedient of changing the oxygen inflow to the column. Instead, the fluid pressurizable section can be actuated to change the cross sectional area of the oxygenating column (and accordingly the volume) in an appropriate manner to maintain the upward velocity of the blood in the oxygenating column at a relatively constant rate, which rate thus becomes independent of the flow rate of blood passing into the column. By this expedient, which can of course be used in conjunction with any desired changes in the oxygen flow rate, the user of the oxygenator of this invention has the capability of providing any desired level of blood oxygenation at varying blood flow rates into the oxygenating column without encountering the undesirable eflects of an excessively low oxygen bubble concentration and upward velocity of the blood in the oxygenation column. This aspect of the invention can be used in both flexible, envelope-type and rigid, casing-type blood oxygenators.

In another aspect of this invention, a fluid pressurizable section of flexible, envelope-type oxygenators can be emplaced in portions of the envelope other than those which define the flow passage, to provide rigidity to the envelope upon pressurization. Accordingly, it becomes an easier matter to set up the envelope oxygenator and a matter of less criticality as to the manner of emplacement, since the inflated portions of the envelope provide dimensional stability to the structure.

In the drawings FIG. 1 is an elevational view of an envelope-type oxygenator utilizing the invention of this application in both aspects as described above, with portions partially broken away for purposes of illustration.

FIG. 2 is a plan view of the inflation device used in conjunction with the oxygenator column prior to attachment of the device as part of the envelope oxygenator, with a portion partially broken away.

FIG. 3 is a sectional view taken along line 3-3 of FIG. 1, showing the fluid pressurizable section associated with the oxygenator column in uninflated condition.

FIG. 4 is a sectional view similar to FIG. 3, showing the same structure in inflated condition for exercising positive control of the cross sectional area of the bloodfilled oxygenator column.

FIG. 5 is an elevational view of a portion of a rigid, casing type oxygenator utilizing the invention of this application, with some portions shown in section.

Referring to the drawings, an envelope-type, plastic film bubble oxygenator is shown to comprise sheets of plastic 10, 12 sealed together in part by heat seals 14, 16. Additional heat seals 18, 20 define a flow passage for blood which includes a blood oxygenating portion 22 and a blood defoaming portion 24. Oxygenating portion 22 is formed in arm 23 of the envelope. Arm 23 is defined by slit 25, which partially separates it from the rest of the envelope.

The upstream part of blood defoaming portion 24 contains conventional defoaming sponge 26, such as spun metal fibers or porous plastic, generally containing an organosilicon defoaming agent. A second part of the defoaming portion comprises tortuous passage 28 to permit the final removal of gas bubbles from the blood. Access to passage 28 is defined through filter member 30, having guide 31 to pass the blood to one end of tortuous passage 28. Gas is carried away from the apparatus through exhaust ports 32 and 34. Pocket 29 provides access for a thermometer or the like.

A stream of blood is introduced through entry ports 36, 38, which can be sealed in a sterile manner until use. Entry port 36 is connected to a source of venous blood to provide the main stream of blood being circulated, while entry port 38 is prOVided for the optional recycling of blood as it is removed from an incision site and recycled to the patient. Exit port 40 at the opposite end of the blood flow passage is adapted to connect with tubing for passing the blood back into the patient.

Seals 39 and 41 close off the flow passage around the entry and exit ports. Tubular sparger 42 is mounted in the bottom of oxygenating column 22 to provide a wide distribution of fine bubbles of oxygen into the flowing blood in the column. Sparger 42 is a cup-like member generally made of porous plastic and typically having an average pore size of about 90 to 140- microns. The interior of sparger 42 is connected to oxygen line 44 in a conventional manner, which line is sealed between sheets and 12 along seal line 18.

Access port 46 is a reinforced slit for permitting blood lines and the like to be run transversely through the envelope oxygenator for securance of the lines and for convenience.

A seal line 48 is formed between sheets 10 and 12 in the form of a closed curve which is generally U-shaped and positioned to follow the periphery of the envelope, to define a fluid pressurizable section 50 in the area defined by seal line 48. Inflation port 52, which is of conventional construction, is provided to permit pressurizable section 50 to be inflated and deflated as desired, typically with compressed air or oxygen. Upon inflation, the entire lower portion of the envelope oxygenator becomes relatively rigid and self-supporting, which greatly facilitates mounting the envelope oxygenator on a frame.

The typical technique of mounting the oxygenator is to slide a rod (not shown) between sheets 10 and 12 horizontally across the top of the oxygenator by placing the rod through openings 54, 56 to provide top support for the envelope oxygenator. Holes 58 are provided so that the sides of the oxygenator can be tied with twine or the like. Seal lines 63' prevent leakage of fluid from pressurizable section 50' out of holes 58-.

FIG. 2 shows a second fluid pressurizable member 59 which is utilizable in accordance with this invention. A second pair of flexible plastic sheets 60, 62 are heatsealed together by heat seal 64 in the form of a closed curve to define a pair of interconnected pressurizable chambers 66, 68. This structure is folded longitudinally along intermediate space 70 between chambers 66, 68, and the folded structure is emplaced with chambers 66, 68 bracketing oxygenation column 22 as best shown in FIGS. 3 and 4. A heat seal line 72 is applied to pressurizable member 59 on each side of oxygenation column 22 to affix member 59 to the envelope oxygenator as an integral part thereof.

Inflation port 74 may be of conventional fabrication, and is used to inflate chambers 66, 68 to control the area of oxygenation column 22 in a manner dependent upon the inflation pressure.

FIG. 4 shows a cross sectional view of column 22, filled with the blood-oxygen mixture 65, with chambers 66, 68 in inflated condition. It can be readily seen that the cross sectional area of column 22 can be controlled during the course of the operation simply by inflating or deflating chambers '66, 68 as desired.

Referring to FIG. 5, a portion of an oxygenator is shown having a rigid housing 74 containing a flow path for blood with an oxygenating portion 22 and a defoaming portion 24 similar to the device of FIGS. 1-4. As in the previous embodiment, blood entry ports 36, 38 are provided, as well as oxygen inlet 44, which leads to a sparger (not shown).

A portion of tortuous passage 28 is shown, although it is contemplated that other designs besides the specific design shown can be used. Outlet 40 is also provided, and inlets 36, 38, and outlet 40 all project outwardly from rigid housing 74 for access thereto.

A rigid pressure chamber 76 is defined in housing 74, having access port 78 leading thereto. Annular rigid supports 79 are carried by pressure chamber 76 and, in turn, carry a flexible elastic tube 80 of silicone rubber of other suitable elastomer which defines the major portion of oxygenation column 22. The elastic tube 80' can carry a plurality (for example, three) of axially disposed rigid stifl'eners 82 on its outer surface, to cause the medial portion of elastic tube 80 to maintain a generally constant transverse dimension.

Accordingly, when pressurizable chamber 76 is pressurized, the diameter of tube 80 will be reduced, typically by collapsing of the central portion of the tube and stretching of the end portions 86 to accommodate said collapsing, to provide oxygenating column 22 with a reduced transverse dimension and volume over a major portion of its length.

Hence, the transverse dimension and volume of the oxygenating column 22 of the oxygenator shown can be adjusted as desired by the simple expedient of pressurization or depressurization of chamber 76. It is, of course, contemplated that a vacuum may be drawn on chamber 76 to expand the oxygenating column 22, if desired.

The above disclosure is offered for purposes of illustration only, and is not to be viewed as limiting the scope of the invention of this application as defined in the claims below.

That which is claimed is:

1. The method of oxygenating blood which comprises introducing blood into a generally vertically disposed, flexible flow passage for blood, introducing a stream of oxygen bubbles into a lower portion of said passage, and removing said blood and oxygen bubbles from said generally vertically disposed passage at an upper portion thereof, the improvement comprising providing pressure to the exterior of said generally vertically disposed passage to positively control the cross sectional dimension of said passage responsive to said pressure.

2. The method of claim 1 in which said pressure is varied in a manner responsive to the flow rate of blood into said passage, to maintain a relatively constant upward velocity of the blood in said passage.

3. The method of claim 2 in which the blood which is removed from said passage is passed through defoaming and debubbling means.

4. A bubble type blood oxygenator which comprises a flexible envelope having sealed portions defining in said envelope a flow passage with a blood oxygenating portion and a blood defoaming portion, and which has means for introducing a stream of blood and a stream of oxygen bubbles into one end of said flow passage, means for removing blood from the other end of said flow passage, and means defining a fluid pressurizable section rendering a portion of said envelope other than the portion defining said flow passage pressurizable, to provide rigidity to said envelope on pressurization.

5. The blood oxygenator of claim 4 in which said fluid pressurizable section is generally U-shaped and positioned to follow the periphery of said envelope.

6. A bubble type blood oxygenator which comprises a body defining a flow passage with a blood oxygenating portion and a blood defoaming portion, and which has means for introducing a stream of blood and a stream of oxygen bubbles into one end of said flow passage, means for removing blood from the other end of said flow passage, and means defining a fluid pressurizable section as part of said oxygenator, positioned along the blood oxygenating portion to variably adjust and positively control the cross sectional area of the oxygenating portion responsive to pressure in said pressurizable section.

7. The blood oxygenator of claim 1 in which said fluid pressnrizable section comprises an elastic tube, the bore of which defines a major part of said blood oxygenating portion of the flow passage, said elastic tube being mounted in a pressurizable chamber with the ends of said tube communicating with the remainder of said flow passage, whereby the cross sectional dimension of said tube is variable in a manner responsive to the pressure in said chamber.

8. The blood oxygenator of claim 7 in which said elastic tube carries longitudinally mounted stiffening members.

9. The blood oxygenator of claim 1 in which said body comprises a flexible envelope.

10. The blood oxygenator of claim 9 further comprising a slit-like access port through said envelope.

References Cited UNITED STATES PATENTS Re. 27,100 3/1971 De Wall 23258.5 3,074,402 1/ 1963 Broman 23-258.5 3,183,908 5/1965 Collins et al 23-258.5 3,276,589 10/1966 Iankay 23258.5 UX 3,332,746 7/1967 Clalf et a1. 23258.5 3,413,095 11/1968 Bramson 23258.5 3,502,440 3/ 1970 Tompkins 2325 8.5 3,526,481 9/1970 Rubricius 23258.5

BARRY S. RICHMAN, Primary Examiner US. Cl. X.R.

23-258.5; 128-DIG. 3; 261-DIG. 28 

